1. Field of the Invention
This invention relates in general to database management systems performed by computers, and in particular, to delayed delivery of query results or other data from a federated server to a federated client until such information is needed.
2. Description of Related Art
The present invention relates to a system and method for representing and searching multiple heterogeneous datastores and managing the results of such searches. Datastore is a term used to refer to a generic data storage facility, such as a relational data base, flat-file, hierarchical data base, etc. Heterogeneous is a term used to indicate that the datastores need not be similar to each other. For example, each datastore may store different types of data, such as image or text, or each datastore may be based on a different theory of data model, such as Digital Library/VisualInfo or Domino Extended Search (DES).
For nearly half a century computers have been used by businesses to manage information such as numbers and text, mainly in the form of coded data. However, business data represents only a small part of the world""s information. As storage, communication and information processing technologies advance, and as their costs come down, it becomes more feasible to digitize other various types of data, store large volumes of it, and be able to distribute it on demand to users at their place of business or home.
New digitization technologies have emerged in the last decade to digitize images, audio, and video, giving birth to a new type of digital multimedia information. These multimedia objects are quite different from the business data that computers managed in the past, and often require more advanced information management system infrastructures with new capabilities. Such systems are often called xe2x80x9cdigital libraries.xe2x80x9d
Bringing new digital technologies can do much more than just replace physical objects with their electronic representation. It enables instant access to information; supports fast, accurate, and powerful search mechanisms; provides, new xe2x80x9cexperientialxe2x80x9d (i.e. virtual reality) user interfaces; and implements new ways of protecting the rights of information owners. These properties make digital library solutions even more attractive and acceptable not only to corporate IS organizations, but to the information owners, publishers and service providers.
Generally, business data is created by a business process (an airline ticket reservation, a deposit at the bank, and a claim processing at an insurance company are examples). Most of these processes have been automated by computers and produce business data in digital form (text and numbers). Therefore it is usually structured coded data. Multimedia data, on the contrary, cannot be fully pre-structured (its use is not fully predictable) because it is the result of the creation of a human being or the digitization of an object of the real world (x-rays, geophysical mapping, etc.) rather than a computer algorithm.
The average size of business data in digital form is relatively small. A banking recordxe2x80x94including a customers name, address, phone number, account number, balance, etc.xe2x80x94represents at most a few hundred characters, i.e. few hundreds/thousands of bits. The digitization of multimedia information (image, audio, video) produces a large set of bits called an xe2x80x9cobjectxe2x80x9d or xe2x80x9cblobsxe2x80x9d (Binary Large Objects). For example, a digitized image of the parchments from the Vatican Library takes as much as the equivalent of 30 million characters (30 MB) to be stored. The digitization of a movie, even after compression, may take as much as the equivalent of several billions of characters (3-4 GB) to be stored.
Multimedia information is typically stored as much larger objects, ever increasing in quantity and therefore requiring special storage mechanisms. Classical business computer systems have not been designed to directly store such large objects. Specialized storage technologies may be required for certain types of information, e.g. media streamers for video or music. Because certain multimedia information needs to be preserved xe2x80x9cforeverxe2x80x9d it also requires special storage management functions providing automated back-up and migration to new storage technologies as they become available and as old technologies become obsolete.
Finally, for performance reasons, the multimedia data is often placed in the proximity of the users with the system supporting multiple distributed object servers. This often requires a logical separation between applications, indices, and data to ensure independence from any changes in the location of the data.
The indexing of business data is often imbedded into the data itself. When the automated business process stores a person""s name in the column xe2x80x9cNAME,xe2x80x9d it actually indexes that information. Multimedia information objects usually do not contain indexing information. This xe2x80x9cmeta dataxe2x80x9d needs to be created in addition by developers or librarians. The indexing information for multimedia information is often kept in xe2x80x9cbusiness likexe2x80x9d databases separated from the physical object.
In a Digital Library (DL), the multimedia object can be linked with the associated indexing information, since both are available in digital form. Integration of this legacy catalog information with the digitized object is crucial and is one of the great advantages of DL technology. Different types of objects can be categorized differently as appropriate for each object type. Existing standards like MARC records for libraries, Finding Aids for archiving of special collections, etc . . . can be used when appropriate.
The indexing information used for catalog searches in physical libraries is mostly what one can read on the covers of the books: authors name, title, publisher, ISBN, . . . enriched by other information created by librarians based on the content of the books (abstracts, subjects, keywords, . . . ). In digital libraries, the entire content of books, images, music, films, etc . . . are available and xe2x80x9cnew contentxe2x80x9d technologies are needed; technologies for full text searching, image content searching (searching based on color, texture, shape, etc . . . ), video content searching, and audio content searching. The integrated combination of catalog searches (e.g. SQL) with content searches will provide more powerful search and access functions. These technologies can also be used to partially automate further indexing, classification, and abstracting of objects based on content.
To harness the massive amounts of information spread throughout these networks, it has become necessary for a user to search numerous storage facilities at the same time without having to consider the particular implementation of each storage facility.
Object-oriented approaches are generally better suited for such complex data management. The term xe2x80x9cobject-orientedxe2x80x9d refers to a software design method which uses xe2x80x9cclassesxe2x80x9d and xe2x80x9cobjectsxe2x80x9d to model abstract or real objects. An xe2x80x9cobjectxe2x80x9d is the main building block of object-oriented programming, and is a programming unit which has both data and functionality (i.e., xe2x80x9cmethodsxe2x80x9d). A xe2x80x9cclassxe2x80x9d defines the implementation of a particular kind of object, the variables and methods it uses, and the parent class it belongs to.
Some known programming tools that can be used for developing search and result management frameworks include IBM VisualAge C++, Microsoft Visual C++, Microsoft Visual J++, and Java.
There is a need in the art for an improved federated system. In particular, there is a need in the art for delayed delivery of query results or other data from a federated server to a federated client until such information is needed.
To overcome the limitations in the prior art described above, and to overcome other limitations that will become apparent upon reading and understanding the present specification, the present invention discloses a technique for delayed delivery of query results or other data from the federated server to federated client until such information is needed.
According to an embodiment of the invention, one or more commands are executed at a client computer to retrieve data from one or more datastores connected to a server computer. At the client computer, a search request is transmitted to the server computer. Then, a client collection generated for use in retrieving physical data from the server computer. When data is requested using the client collection, physical data is retrieved from the server computer.